Method and apparatus for defined magnetizing of permanently magnetizable elements and magnetoresistive sensor structures

ABSTRACT

A method of magnetizing a permanently magnetizable element associated with a magnetic field sensor structure includes generating a test magnetic field penetrating the magnetic field sensor structure and the permanently magnetizable element, detecting the magnetic field and providing a test signal based on a magnetic field through the magnetic field sensor structure, aligning the test magnetic field and the magnetic field sensor structure with the permanently magnetizable element to each other, until the test signal reaches a set value corresponding to a predetermined magnetized field distribution with respect to the magnetic field sensor structure, and generating a magnetizing field for permanently magnetizing the element to be permanently magnetized, wherein the magnetizing field corresponds to the predetermined magnetic field distribution within a tolerance range.

This application claims priority to German Patent Application 10 2007029 665.9, which was filed Jun. 27, 2007 and is incorporated herein byreference.

BACKGROUND

The present invention relates to a method and an apparatus formagnetizing a permanently magnetizable element associated with amagnetic field sensor structure, for monitoring the alignment of amagnetic field, to an arrangement of a magnetic field sensor elementwith a permanently associated, non-magnetized hard magnetic materialstructure, as well as to a method of inscribing a magnetization into amagnetoresistive sensor structure and for protecting a sensor structureagainst external magnetic fields.

Magnetic field sensors are used, for example, for incremental velocitymeasurement or as angle sensors. Therefore, frequently magnetoresistive(MR) or giant magnetoresistive (GMR) sensor chips are used, which candetect a change of an external magnetic field. This external magneticfield can be generated, for example, in angle sensors, by a so-calledmagnetic field, which is mounted above the sensor chip on a shaft/axis.Rotating metal wheels or perforated discs are frequently used forgenerating a required magnetic field deflection when using magneticfield sensors for velocity measurement. In this case, a back-biasmagnet, which is generally behind the magnetic field sensor, generatesthe magnetic field to be deflected.

In any case, the exact positioning of the magnet generating the externalmagnetic field, such as the back-bias magnet or the magnetic pill, andthe exact direction of magnetization in relation to the magnetic fieldsensor structure, such as the MR/GMR sensor chip in the above-mentionedexample, are of significant importance for an exact mode of operation.

SUMMARY OF THE INVENTION

According to embodiments, the present invention provides a method and anapparatus for magnetizing a permanent magnetizable element associatedwith a magnetic field sensor structure by generating a test magneticfield, which penetrates the magnetic field sensor structure and thepermanently magnetizable element, by detecting the test magnetic fieldand providing a test signal based on the test magnetic field by themagnetic field sensor structure, for aligning the test magnetic fieldand the magnetic field sensor structure with a permanently magnetizableelement to each other, until the test signal reaches a set valuecorresponding to a predetermined magnetic field distribution withrespect to the magnetic field sensor structure, and for generating amagnetizing field for permanently magnetizing the permanentlymagnetizable element, wherein the magnetizing field corresponds to thepredetermined test magnetic field within a tolerance range.

According to further embodiments, the present invention provides amethod and an apparatus for inscribing a defined magnetization into amagnetoresistive sensor structure, an arrangement of a magnetic fieldsensor element with a permanently associated, non-magnetized hardmagnetic material structure, a method and an apparatus for protectingthe magnetization of a magnetoresistive sensor structure against anexternal magnetic field, as well as a method of monitoring the alignmentof a reference magnetic field in relation to a magnetic field sensorstructure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the accompanying drawings, in which:

FIG. 1 is a flow diagram for the method of magnetizing a permanentlymagnetizable element associated with a magnetic field sensor structure;

FIGS. 2 a and 2 b are a schematic cross-sections of a magnetic fieldsensor structure with the magnetic field lines of a back-bias magnet;

FIG. 3 a is a schematic cross-sectional image of an apparatus formagnetizing a permanently magnetizable element associated with amagnetic field sensor structure;

FIG. 3 b is a schematic cross-sectional image of another embodiment ofan apparatus for magnetizing the permanently magnetizable elementassociated with a magnetic field sensor structure;

FIG. 3 c is a schematic cross-sectional image of a further embodiment ofan apparatus for magnetizing a permanently magnetizable elementassociated with a magnetic field sensor structure;

FIG. 4 is a flow diagram of the method of inscribing a definedmagnetization into a magnetoresistive sensor structure of a magneticfield sensor arrangement;

FIG. 5 is a schematic side view of a magnetic field sensor chip arrangedin a housing;

FIG. 6 is a flow diagram of the method of monitoring the alignment of amagnetic field of a reference magnet with respect to a magnetic fieldsensor arrangement;

FIG. 7 is a schematic cross-sectional image of a rotation angle sensorhaving a magnetic field sensor chip and associated therewith apivot-mounted magnetic pill; and

FIG. 8 is a schematic top view of a magnetic field sensor chip with chipcarrier frame and chip pins.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

With reference to FIGS. 1 to 8, embodiments of the method and apparatusfor magnetizing a permanently magnetizable element associated with amagnetic field sensor structure, for monitoring the alignment of amagnetic field as well as for inscribing a magnetization intomagnetoresistive sensor structure and for protecting a sensor structureagainst external magnetic fields will be discussed in detail below.

With regard to the following description of the embodiments of thepresent invention it should be noted that for simplification, the samereference numbers are used throughout the description for functionallyidentical and analog or equivalent elements, respectively.

With reference to FIG. 1, the method of magnetizing a permanentlymagnetizable element associated with a magnetic field sensor structurewill be discussed in detail. In the context of this invention,“associated” can also mean “permanently connected” or also “arranged ina spaced way”. The permanently magnetizable element can be a hardmagnetic material having a high coercive field strength and thus havinghigh resistance against external magnetic fields. Such hard magneticmaterials can be magnetized permanently as permanent magnets by theimpact of a sufficiently strong magnetic field. A permanent magnet is apiece of magnetizable material, such as iron, cobalt or nickel, whichmaintains its static magnetic field without having to supply energyconstantly, such as in contrast to electromagnets.

The method comprises (step 10) generating a test magnetic fieldpenetrating the magnetic field sensor structure and the permanentlymagnetizable element, detecting (step 12) the test magnetic field andproviding a test signal based on the test magnetic field by the magneticfield sensor structure, aligning (step 14) the test magnetic field andthe magnetic field sensor structure with the permanently magnetizableelement, until the test signal reaches a set value corresponding to apredetermined magnetic field distribution with respect to the magneticfield sensor structure, and generating (step 16) a magnetizing field forpermanently magnetizing the permanently magnetizable element, themagnetizing field corresponding to the predetermined magnetic fielddistribution within a tolerance range.

Generating (step 10) a test magnetic field penetrating the magneticfield sensor structure and the permanently magnetizable element can, forexample, be achieved by electrical excitation of a coil arrangementhaving one or several current-carrying air or conductor coils,respectively, and having the magnetic field sensor structure and thepermanently magnetizable element positioned in its magnetic field.

Detecting (step 12) the test magnetic field and providing a test signalbased on the test magnetic field by the magnetic field sensor structurecan, for example, be performed with magnetoresistive sensors, such astunnel magnetoresistance (TMR), anisotropic magnetoresistance (AMR) orgiant magnetoresistance (GMR) sensor structures. The usage of othermagnetic field sensor structures, such as Hall probes, colossalmagnetoresistance (CMR) sensors, magnetic resistors, magnetotransistors,giant planar Hall effect sensors, spin transistors, giant magneticimpedance (GMI) elements or magnetic field diodes is also possible.However, it should be noted that the above list is not exhaustive andthus represents no limitation with regard to the invention.

The magnetic field sensor can have, for example, a test output, viawhich the test signal based on the test magnetic field can be read out.Further, magnetic field auxiliary sensor structures can be placed on themagnetic field sensor structure, whose measurement values are only readout during the inventive method. Further magnetoresistive sensorstructures that can, for example, measure the magnetic field componentorthogonal to the normal measurement field direction in the magneticfield sensor structure plane, and/or, for example, Hall sensors that candetect the magnetic field component perpendicular to the magnetic fieldsensor structure plane, can be arranged as magnetic field auxiliarysensor structures.

Hall sensors have, for example, the advantage that they, due to thenon-existing saturation, provide a signal from which in any case agradient can be established for determining the optimum position foraligning the magnetic field and the magnetic field sensor structure withthe permanently magnetizable element.

The magnetic field sensor structure can also have two or more sensorelements, which are then used for detecting the test magnetic field andalso for providing the test signal based on the test magnetic field. Themagnetic field sensor structure can have, for example, a test mode inwhich measurement values of the difference in voltage of the sensorelements forming a bridge circuit or also a voltage of individual sensorelements, such as the voltage of the right and left so-called halfbridges, can be read out individually.

Aligning (step 14) the test magnetic field and the magnetic field sensorstructure with the permanently magnetizable element to each other can beperformed in different ways. The magnetic field sensor structure and theassociated permanently magnetizable element can, for example, be alignedwith respect to an existing test magnetic field. For example, themagnetic field sensor structure with the associated permanentlymagnetizable element can be moved in a fixedly positioned coilarrangement consisting of one or several current-carrying air/conductorcoils for generating the test field in such a way in the magnetic fieldof the coil arrangement that the test signal reaches a certain set valuecorresponding to a predetermined magnetic field distribution withrespect to the magnetic field sensor structure. By changing thealignment of the magnetic field sensor structure in the test magneticfield, a change of the test signal can be achieved, and thus the spatialpositioning of the magnetic field sensor structure with the associatedpermanently magnetizable element up to a predetermined set value can beachieved. After reaching the set value and thus the spatial positioningof the magnetic field sensor structure with the associated permanentlymagnetizable element in the test magnetic field, the magnetizing fieldfor permanently magnetizing the permanently magnetizable element can begenerated. Thereby, the magnetizing field can correspond to thepredetermined magnetic field distribution of the test magnetic fieldwithin a tolerance range. The tolerance range or the possible deviationbetween the magnetizing field and the test magnetic field, respectively,can, for example, be less than 20%, 10%, 5% or 3% and should be as lowas possible. So that the magnetic field and the test magnetic field havean appropriate field distribution, they can both be generated by thesame coil arrangement with one or several current-carrying air/conductorcoils. The magnetizing field can be large enough to magnetize thepermanently magnetizable material deeply into the saturation to generatea permanently magnetized element. When turning off the magnetizingfield, the permanently magnetizable element has a permanent magneticfield in the size of the so-called remanence. Thus, the permanentlymagnetizable element can represent a future permanent magnet. Themagnetization can be performed by pulse-like application of a highmagnetizing field with the help of an electromagnet. The test magneticfield can have a magnetic field strength smaller than the magnetizingfield strength required to permanently magnetize the permanentlymagnetizable material. The test magnetic field can be applied across alonger time period since the same performs the positioning of themagnetic field sensor structure with the arranged permanentlymagnetizable element. The test magnetic field can, for example, be inthe order of magnitude of the back-bias magnet required for thefunctioning of the magnetic field sensor structure for incrementalvelocity measurement, or also in the order of magnitude of the magneticfield of a magnetic pill required for the functioning of a rotationangle sensor.

The magnetic field sensor structure with the arranged permanentlymagnetizable element can, for example, be a magnetoresistive sensor,which is firmly connected to the back-bias magnet for a magnetic fieldsensor for incremental velocity measurement. When using magnetic fieldsensors for incremental velocity measurement, rotating metal wheels orperforated discs are frequently used for generating the requiredmagnetic field deflection. A back-bias magnet, which is normally behindthe magnetic field sensor, generates the magnetic fields to bedeflected. As has already been noted above, the positioning accuracy ofthe magnet can cause sensitivity variations, for example, between thesensor elements of a differential measurement arrangement on themagnetic field sensor structure, and an offset in the velocitymeasurement. Further, inaccuracies in the positioning of the system of aback-bias magnet and magnetic field sensor in front of the gear areadded to this. In magnetoresistive sensors, mispositioning can have theeffect that magnetic field changes through the gear are detected in sucha different way at different positions on the magnetic field sensorstructure with regard to offset, sensitivity, phase position andsaturation effects that a differential measurement can no longer beinterpreted in a meaningful way. Thus, exact positioning of the magneticfield sensor structure with respect to the back-bias magnet generallylying behind the sensor structure is desired. Therefore, a permanentlymagnetizable element can be mounted in a chip housing together with themagnetic field sensor structure. The alignment of the magnetic fieldsensor structure in fixed connection with the future magnet in themagnetizing field can then be made such that the magnetic field sensorstructure is operated in a weaker test magnetic field, which is alsogenerated by the magnetizing means, and the magnetic field sensorstructure uses output signals for optimizing the position prior togenerating the strong magnetizing field. As has already been describedabove, for improving the positioning accuracy, the magnetic field sensorstructure can also have a test output, via which the field strengthmeasurement values of the magnetic field sensor structure can be readout if the output normally only provides switching signals. Byintroducing magnetic field auxiliary sensor structures, the alignment ofthe magnetic field sensor structure in fixed connection to the futuremagnet can be optimized in the test and magnetizing field.

Then, the permanently magnetizable element, for example the back-biasmagnet, still to be magnetized can then be integrated into a chiphousing or integrated circuit (IC), respectively, together with themagnetic field sensor structure. The magnetization of the permanentlymagnetizable element or the back-bias magnet, respectively, can then beperformed after a functional test of the respective chip functionality.This has the advantage that the tests, for example, so-called back endtests, can be performed at non-magnetic devices and thus with standardtest and process equipment. Possible placing tolerances in theintegration into the chip housing can then be compensated by theabove-described method. Magnetization of the back-bias magnet can thenbe performed, for example, only after the overall module or assemblysetup with the respective magnetic field sensor chip.

An arrangement of a magnetic field sensor and a non-magnetized hardmagnetic material can thus be arranged in a common package or component,respectively. Thereby, the hard magnetic material can be determined tobe subsequently magnetized to a permanent magnet after it is firmlyfixed to the magnetic field sensor, wherein its magnetization forgenerating the back-bias magnetization can be individually aligned inrelation to the magnetic field sensor.

For carrying out the adjustment of the magnetizing field for theback-bias magnet, a test magnetic field in the order of magnitude of thefield that the back-bias magnet should have after the magnetization canbe generated, for example, with the magnetizing coil arrangement. Withthis test magnetic field, different variations can be performed, whichallow to determine the required variation of magnetization of theback-bias magnet for the best possible compensation of placing andarrangement tolerances. FIGS. 2 a/2 b show schematically the back-biasmagnet 22, its field distribution 18 and the magnetic field sensorstructure 20, which can, for example, be a magnetoresistive sensorstructure, where the magnetic detection plane corresponds to the sensorstructure plane. As shown in FIGS. 2 a/2 b, the magnetic field sensorstructure 20 can have, for example, two sensor elements 21, which woulddetect a different magnetic field strength at a mispositioning of themagnetic field sensor structure 20 in relation to a back-bias magnet 22with its constant magnetic field line distribution 18, which can causeinaccuracies, for example, in a differential measurement.

As can be seen in FIGS. 3 a-c, the permanently magnetizable element, inthis case the back-bias magnet 22, can have a different shape adapted tothe respective requirement for generating the permanent magnetic field.

The set value corresponding to a predetermined magnetic fielddistribution with respect to the magnetic field sensor structure can bechosen, for example, such that the field distribution of the testmagnetic field, and thus the magnetizing field, and thus the magneticfield of the permanently magnetized element, is perpendicular to themagnetic detection plane within a tolerance range. Again, the tolerancerange can, for example, be less than 20%, 10%, 5% or 3%.

FIGS. 3 a-c show schematically the means for aligning the test magneticfield and the magnetic field sensor structure with the permanentlymagnetizable element to each other. The means can have, for example, acoil arrangement 24 consisting of one or several air/conductor coils 30a-30 c implemented as electromagnets, i.e., when the coil arrangementcarries a current, a magnetic field is generated within the coilarrangement. Further, FIG. 3 a shows schematically that the component 23wherein the magnetic field sensor structure 20 is integrated in fixedconnection to the permanently magnetizable element and the futureback-bias magnet 22, respectively, can be moved within a magnetic fieldnot shown in the figure by a horizontal movement 26 or also a tiltingmovement 28. Aligning the component 23 in the test magnetic fieldgenerated by the coil arrangement 24 is performed until the test signalcorresponds to a set value, which then corresponds to a predeterminedmagnetic field distribution in the magnetic field sensor structure.Aligning the test magnetic field generated by the coil arrangement 24and the magnetic field sensor structure 20 with the permanentlymagnetizable element 22 can also be performed such that the coilarrangement consists of several air/conductor coils 30 a-30 c which cangenerate a variable test and later magnetizing field. The variation ofthe target frequency can be performed until the test signal correspondsto the desired set value.

The terminals for the output of the test signals of the magnetic fieldsensor structure 20 are not illustrated in the schematical figures.

FIG. 3 c shows a further embodiment in a schematic image. Apart from thecoil arrangement 24 and the component 23 with the magnetic field sensorstructure 20 and the permanently magnetizable element 22, a spatiallypositionable soft magnetic element 32 can be in the magnetic field ofthe coil arrangement 24. By a movement of the soft magnetic element 32serving as a core for focusing the magnetic field lines of the coilarrangement 24, the magnetic field of the coil arrangement 24, forexample, the test magnetic field, can be altered such that the testsignal of the magnetic field sensor structure 20 corresponds to the setvalue. In this position, the stronger magnetizing field can be generatedby the coil arrangement 24 to permanently magnetize the permanentlymagnetizable element.

During the alignment of the test magnetic field and the magnetic fieldsensor structure to each other, the magnetic field sensor structure canbe simultaneously be tested for its functionality, since the magneticfield sensor structure should provide respective test signals. Thismeans, test time can possibly be saved in the further productionprocess.

The above-described method can, for example, also be used formagnetizing a so-called magnetic pill in a rotation angle sensor with aMR/GMR sensor structure. Such a rotation angle sensor with a MR/GMRsensor structure is illustrated schematically in FIG. 7 as embodiment ofthe invention. A so-called magnetic pill 42 is arranged at the end of apivot-mounted axis 36 and is non-magnetized at first. A MR/GMR sensorstructure is arranged at a distance of, for example, 0.5 mm to 5 mmbelow the magnetic pill, wherein the detection plane of the sensorstructure is perpendicular to the rotation axis of the magnetic pill.The MR/GMR sensor structure with a Hall probe as magnetic fieldauxiliary sensor structure is realized in a silicon chip 44. The siliconchip 44 is mounted in a housing 60 with chip pins 68. The sensor chipcan, for example, be adhered or soldered to a printed circuit board 50,which is again mounted in an appropriate way via mounting posts 52 of aprinted circuit board 50 to a housing part or frame 34, which at thesame time comprises the ball bearing 38 for the rotation axis 36. Themagnetic pill, which is non-magnetized at first, is only magnetizedafter all parts of the system, at least the rotation axis 36 includingbearing 38, the magnetic pill 42 of the sensor chip and its terminalsare mounted and possibly molded. For magnetizing the magnetic pill inthe rotation angle sensor, the above-described method of magnetizing apermanently magnetizable element, here the magnetic pill, can also beperformed. There, the test magnetic field in the magnetizing field havethe magnetic field distribution predetermined by the set value within atolerance range.

For permanently magnetizing the magnetic pill, the permanentlymagnetizing material of the magnetic pill is saturated by a strongexternal magnetizing field generated by the magnetizing coils 40.Normally, the magnetic field is generated by an air/conductor coil,consisting of a few thick copper turns, by sending a short strongcurrent pulse through the coil. There, the field has to be about threeto five times larger than the coercivity of the permanently magnetizableelement. Depending on the used permanently magnetizable material, thecurrents in the copper turns of the coil arrangement can be 250 kA/m forAlNiCo up to 5 MA/m for NdDyFeB. For generating such large magneticfields, the coil arrangement can be operated in a pulsed way. The pulsescan be very short, since otherwise the power dissipation transformed inthe coil arrangement can cause fusing of the same or can cause asoftening, and this can result in a form change due to the powers.

In angular sensors, as they are exemplarily described in FIG. 7, MR/GMRsensor chips are frequently used, which detect the direction of themagnetic field generated by a magnetic pill 42, which is again mountedon a shaft/axis 36. If, however, the direction of the magnetization ofthe magnetic pill is not perfectly parallel to the MR/GMR sensor chipdetection plane, an angle error occurs. Reason for this non-parallelityare various position tolerances. The magnetization of the magnetic pillmight not be perfect to the surface of the pill, the pill might not bemounted perfectly perpendicular to the rotation direction, since, forexample, the adhesive holding the magnetic pill from the rotation axishas no uniform thickness or the MR/GMR sensor chip has not been solderedon the mount in a perfectly perpendicular way to the rotation directionof the magnetic pill, or, since, for example, its pins float unevenly onthe soldering tin, the sensor chip housing has a slightly wedge-shapedgeometry, and the adhesion of the chip on the chip carrier frame has awedge-shaped form. Even the silicon, in which the magnetic field sensorstructure is realized, might not be polished in a perfectly planar way,or the magnetization of the MR/GMR sensor chip is not perfectly parallelto the silicon surface since the inscription process of themagnetization is prone to tolerances. These arrangement errors can bereduced by the above-described inventive methods, so that the accuracy,for example, of angular measurement, can be increased.

With reference to FIG. 4, the method of inscribing a definedmagnetization into a magnetoresistive sensor structure of a magneticfield sensor arrangement further having a magnetic field auxiliarysensor structure, is illustrated in a flow diagram. The method includes(step 51) generating a test magnetic field penetrating the magneticfield sensor arrangement, further detecting the test magnetic field andproviding the test signal (step 53) based on the test magnetic field bythe magnetic field auxiliary sensor structure, further aligning (step54) the test magnetic field and the magnetic field sensor arrangement toeach other until the test signal reaches a set value corresponding to apredetermined magnetic field distribution in the detection plane of themagnetic field auxiliary sensor structure. Additionally, the methodincludes heating (step 57) of the magnetoresistive sensor structure toan inscription temperature and generating a magnetic field (step 58) forpermanently inscribing the magnetization into the magnetoresistivesensor structure, wherein the magnetizing field has a predeterminedcorresponding magnetic field distribution within a tolerance range.

The magnetoresistive sensor structure can be, for example, ananisotropic magnetoresistance (AMR), a giant magnetoresistance (GMR) ora tunnel magnetoresistance (TMR) sensor structure.

Generating a test magnetic field can again be performed by a coilarrangement with one or several current-carrying conductor coils.Detecting the test magnetic field and providing a test signal (step 53)based on a test magnetic field is performed by the magnetic fieldauxiliary sensor structure that can, for example, be arranged below themagnetoresistive sensor structure. The magnetic field auxiliary sensorstructure can, for example, be a Hall probe, which can then be arrangedsuch that the magnetic detection plane of the Hall probe isperpendicular to the magnetoresistive sensor structure to be magnetized.

Aligning (step 54) the test magnetic field and the magnetic field sensorarrangement to each other can be performed such that the coilarrangement generating the test magnetic field is adjusted such that thetest signal of the magnetic field auxiliary sensor structure assumes acertain set value corresponding to a certain magnetic field distributionin the detection plane of the magnetic field auxiliary sensor structure.Since the magnetic detection plane of the magnetic field auxiliarysensor structure and the magnetic detection plane have a fixed angulardependence, a certain alignment of the test magnetic field to themagnetic detection level of the magnetoresistive sensor structure can beobtained. The magnetic detection plane of the magnetic field auxiliarysensor structure, for example, a Hall sensor, can stand perpendicular onthe magnetoresistive sensor structure, and the set value can be definedsuch that the test magnetic field stands perpendicular to the magneticdetection plane of the magnetic field auxiliary sensor structure andthus, the test magnetic field is aligned in parallel to themagnetoresistive sensor structure chip area.

After aligning the test magnetic field and the magnetic fieldarrangement to each other, such that the test signal corresponds to theset value, the magnetoresistive sensor structure can be heated to aninscription temperature (step 57). The exact inscription temperaturedepends on the used materials of the magnetoresistive sensor structure.The inscription temperature can, for example, be higher than 200° C. andcan be approximately 250° C. Generating a magnetizing field (step 58)for permanently inscribing the magnetization into the magnetoresistivesensor structure can then again be performed by a coil arrangementhaving one or several current-carrying air coils. Thus, the coilarrangement for generating the magnetic test field and for generatingthe magnetizing field can be identical. Inscribing a definedmagnetization into the magnetoresistive sensor structure can only beperformed at a corresponding heating of the sensor structure. Heatingcan be performed in an oven designed for this process, or, for example,by locally heating the magnetoresistive sensor structure with a laser.It is also possible to perform detecting the test magnetic field andproviding the test signal based on the test magnetic field by themagnetic field auxiliary sensor structure, such as a Hall sensor, andaligning the test magnetic field and the magnetic field sensorarrangement to each other during heating the magnetoresistive sensorstructure or also at the respective inscription temperature.Alternatively, it is also possible to operate the Hall sensor even at,for example, 250° C., since the same is relatively robust against hightemperatures. In local heating during the inscription process, a layoutand circuit design should be chosen that can buffer a high temperaturegradient. It is possible that in simple systems for determining theposition of the magnetoresistive sensor structure with respect to themagnetic field direction of the test magnetic field, a magneticalternating field is applied, because then the offset resulting in aHall probe can be neglected, which simplifies the circuit technology.

It is also possible to use the above-described method of inscribing adefined magnetization for a wafer comprising a plurality of magneticfield sensor arrangements, and thus a plurality of magnetic field sensorarrangements can be magnetized simultaneously in a defined way.

In order to determine in the above-described method whether the angularposition is sufficiently exact during the alignment of the test andmagnetizing field, the magnitude of the magnetic field strength in theplane of the magnetoresistive sensor structure should be known. This canbe obtained by calibrating the magnetic system for inscribing.Inaccuracies of several percent can be tolerated. Additionally, themagnetic sensitivity of the Hall probe should be given. With knownself-compensation methods, the measurement inaccuracy in Hall probes canbe reduced to several percent. Additionally, it should be consideredthat the Hall probe output signal remains below a predetermined limit inorder to guarantee the direction of the magnetic field sufficiently nearin the magnetoresistive sensor structure surface.

The magnetic system generating the test and magnetizing field can, forexample, be rotated in the range of several angular degrees around theintended ideal position for inscribing the defined magnetization intothe magnetoresistive sensor structure, and several test signals of themagnetic field auxiliary sensor structure can be accepted. From that, acurve can be extracted, which passes through a zero line, wherein thezero crossing represents an ideal angular position of the magneticsystem, which can then be calculated, and can be introduced into themagnetoresistive sensor structure for inscribing defined magnetization.Possibly, it can be advantageous to operate without alternating themagnetic field and with the so-called spinning current method, sincethen the lateral Hall effect is averaged out, and thus the accuracy ofthe angular adjustment of the magnetic system can be increased.Normally, the Hall probe has an offset that can be spurious in themeasurement of a magnetic field. The Hall probe can be operated in theknown spinning current method to separate the offset from the fieldportion. Also, an operation is possible where the Hall probe determinesits offset in a calibration phase, in order to be able to measure thefield with a bandwidth as high as possible in a subsequent measurementphase, without time-discrete signal processing.

Since the magnetization in the magnetoresistive sensor structure alignsitself with respect to the applied magnetic field at the respectiveinscription temperature and is “eternalized” there, when this magneticfield is not exactly parallel to the magnetoresistive sensor structuresurface due to mounting tolerances, this angular error can betransferred to the magnetoresistive sensor structure and remains as aninaccuracy factor during further usage of the magnetoresistive sensorstructure. Thus, it can be advantageous when it is tested with anintegrated magnetic field auxiliary sensor structure in the magneticinscription process into the magnetoresistive sensor structure, asdescribed above, whether the applied test or magnetizing field,respectively, stands sufficiently well, e.g., perpendicular on themagnetic field auxiliary sensor structure.

FIG. 5 shows exemplarily a schematic cross-section of a magnetic fieldsensor arrangement 67 consisting of a silicon chip having a Hall probe64 and an MR/GMR sensor structure 62 above the same. The magnetic fieldsensor arrangement 67 is connected on a chip frame carrier or leadframe, respectively, 70 with an adhesive or die attach film 66,respectively. In the side view, the chip carrier frame 70 has chip pinson both sides for further electrical contacting 68. The magnetic fieldsensor arrangement 67 is arranged in a housing 60. In the side view ofthe magnetic field sensor arrangement in a sensor chip illustrated inFIG. 5, the magnetoresistive layer for detecting the direction ofmagnetic fields is in the plane of the MR/GMR sensor structure, whichmeans parallel to the sensor chip surface. In FIG. 5, a conventionalHall probe 64 for detecting magnetic fields perpendicular to the sensorchip surface is immediately below, which means in FIG. 5 in a verticaldirection to the sensor chip surface.

For magnetoresistive sensor structures, a strong magnetizing field, suchas it is required in magnetizing a permanently magnetizable element, canbe damaging, since it can affect the magnetization of themagnetoresistive sensor structure layer. New MR/GMR sensor structurescan withstand much higher fields at room temperature as they are usedfor inscribing at an inscription temperature of, for example, 250° C.,but small changes at the MR/GMR characteristic curve cannot beprecluded. Particularly since it is no longer possible or economical toadjust a complete module with an MR/GMR sensor structure in a widetemperature range or recalibrate the same, respectively.

For avoiding damage of the magnetoresistive sensor structure by a toostrong magnetizing field for permanent magnetization of the permanentlymagnetizable element, the method of protecting a sensor arrangement witha sensor chip against an external multi-magnetic field can be performed.This method cannot only be applied to magnetoresistive sensor structuresbut to all sensor structures or functional chips that can be damaged byan external magnetic field. The method comprises generating a secondarymagnetic field opposing the external primary magnetic field at thesensor chip.

Generating an opposing secondary magnetic field can, for example, beperformed such that a compensation coil is placed around the sensorchip, which is carrying a current proportional to the external primarymagnetic field, in order to generate an opposing secondary magneticfield at the sensor chip. If the external primary magnetic field is, forexample, generated by a coil arrangement, both coils can be connected inseries and can carry the same current when the coil arrangement forgenerating the magnetizing field has more turns than the compensationcoil at the sensor chip, so that the magnetic field sensor chip ismainly extinguished. It is also possible to perform generating theopposing secondary magnetic field at the sensor chip such that a currentflows through the chip carrier frame shown in FIG. 8 which generates amagnetic field tangential to the sensor chip surface. FIG. 8 shows theschematical top view of the magnetic field sensor arrangement 67, forexample, consisting of silicon with the MR/GMR sensor structure 62 andthe underlying Hall probe 64 mounted on the chip carrier frame 70.Additionally, the sensor chip has eight chip pins (pin 1 to pin 8),wherein the pins 1, 4, 5 and 8 are formed such that they can be used tosend a large current through the metallic chip carrier frame 70, whichcan generate a secondary magnetic field at the MR/GMR sensor chipopposing the magnetizing field, which means the primary magnetic field.Pins 2, 3, 7 and 6 are conventional pins via which the sensor chip iscontacted with bond wires. It is also possible that a connection toground of the chip is provided via a bond connection between one orseveral of the pins 1, 4, 5, 8. In the top view in FIG. 8 the MR/GMRsensor is only illustrated schematically as an unitary area. Normally,such MR/GMR sensors are mostly designed in a serpentine shape and aredivided into several sub-units, for example, in order to be able toperform differentiation of the magnetic field components in X and Ydirection in the detection plane of the magnetic field sensor.

As can be seen in FIGS. 5 and 8, the Hall probe should be positioned asclose as possible to the MR/GMR sensor chip to detect the field there.Additionally, it can be space-saving when the MR/GMR sensor chip issputtered on the chip, leaving the area below the MR/GMR sensor chipavailable, which can then be used for forming, for example, theabove-mentioned Hall probe. In the chip carrier frame shownschematically in FIG. 8, the current for generating the secondarymagnetic field can flow horizontally between pins 4 and 5 or 1 and 8,respectively, or also vertically between pins 1 and 4 or 8 and 5,respectively.

A further possibility for generating a secondary magnetic field opposingan external primary magnetic field can be realized by using ashort-circuit turn around of the sensor arrangement with the sensorchip. Generating the opposing secondary magnetic field is therebyperformed such that when an external primary magnetic field is appliedquickly, a magnetic flow flows through the short-circuit turn, such thatits flow change generates a magnetic field opposing the primary magneticfield, according to Lenz's law. This means, the MR/GMR sensor chipmounted below the pill can be protected by a short-circuit turn in thepulse-like strong applied external magnetizing field for theabove-mentioned magnetic pill. This short-circuit turn can possiblyalready be integrated in the sensor chip, by surrounding the sensor inthe chip housing at all sides with metal, for that purpose, for example,a further metal sheet fully covering and slightly overlapping the sensorcan be deposited below and above the sensor. The two metallic sheets canthen be connected, for example, with dense so-called via contact rows,wherein the provided metallic conductor structure can be connected toground of the sensor chip to ensure a defined potential. Since thecross-sectional area of this flat metallic short-circuit turn is small,the magnetic flow change is also small, and thus the currents aresufficiently small so that the metallic sheets are not overloaded. Inthe operation of the sensor, such as the MR/GMR sensor, they do notinterfere, as long as the angular measurement, for example, is performedat sufficiently small currents. It is also possible that the side edgesof the upper and lower metal sheets are not short-circuited directly viavia contact rows, but are connected to each other via a transistor, forexample an n-metal oxide semiconductor (n-MOS) transistor. This nMOStransistor can be turned on only for magnetizing the magnetic pill andcan remain switched off during normal operation in order to not reducethe bandwidth of the system by eddy currents.

The arrangement of a magnetic field sensor and a non-magnetized hardmagnetic material that are arranged in a common package or component asan arrangement or module, respectively, and where the hard magnetic isstill to be magnetized, can have one of the above-described apparatuses,such as a protection coil.

FIG. 6 shows a flow diagram for the method of monitoring the alignmentof a magnetic field of a reference magnet with respect to a magneticfield sensor structure arrangement. The method comprises detecting themagnetic field penetrating the magnetic field sensor arrangement,providing a reference signal (step 80) based on the magnetic field ofthe reference magnet by a magnetic field auxiliary sensor structure, anddetermining the deviation of the alignment of the magnetic field of areference magnet in relation to the magnetic field sensor arrangement bycomparing (step 82) the reference signal to a set signal correspondingto a predetermined magnetic field distribution in the detection plane ofthe magnetic field auxiliary sensor structure.

The magnetic field auxiliary sensor structure can be a Hall sensor andthe magnetoresistive sensor structure can be the above-mentioned AMR,TMR, GMR sensor structures. In the rotation angle sensor schematicallyillustrated in FIG. 7, the reference signal of the magnetic fieldauxiliary sensor structure, in FIG. 7, for example, of a Hall sensor,can be monitored, and when a predetermined limit is exceeded, an errorsignal is output, because the either magnetic interference fieldsdistort the angular measurement or an intolerable tilting of therotation axis of the magnetic pill to the detection plane of the MR/GMRsensor structure exists. By comparing the reference signal with a setsignal, an interference of the magnetic field running in the MR/GMRstructure plane required for an exact mode of operation of the rotationangle sensor can be monitored.

It should be noted that the generation of a secondary magnetic fieldopposing an external primary magnetic field for protecting a sensor chipin a sensor arrangement is more effective the closer the coil-likearrangement for generating the secondary magnetic field can be appliedto the sensor chip, without having to accept a strong feedback of thesecondary coil, for example on the magnetic pill.

While this invention has been described in terms of several advantageousembodiments, there are alterations, permutations, and equivalents whichfall within the scope of this invention. It should also be noted thatthere are many alternative ways of implementing the methods andcompositions of the present invention. It is therefore intended that thefollowing appended claims be interpreted as including all suchalterations, permutations, and equivalents as fall within the truespirit and scope of the present invention.

1. A method of magnetizing a permanently magnetizable element associatedwith a magnetic field sensor structure, the method comprising:generating a test magnetic field penetrating the magnetic field sensorstructure and the permanently magnetizable element; detecting the testmagnetic field and providing a test signal based on the test magneticfield by the magnetic field sensor structure; aligning the test magneticfield and the magnetic field sensor structure with the permanentlymagnetizable element, until the test signal reaches a set valuecorresponding to a predetermined magnetic field distribution withrespect to the magnetic field sensor structure; and generating amagnetizing field for permanently magnetizing the permanentlymagnetizable element, wherein the magnetizing field corresponds, withina tolerance range, to the predetermined magnetic field distribution. 2.The method according to claim 1, wherein generating a test magneticfield is performed such that a coil arrangement, which comprises one orseveral conductor coils and in which the magnetic field sensor structureand the permanently magnetizable element are arranged, is electricallyexcited.
 3. The method according to claim 2, wherein aligning the testmagnetic field and the magnetic field sensor structure with thepermanently magnetizable element is performed such that either the coilarrangement is aligned with the permanently magnetizable element withrespect to the magnetic field sensor structure, or the magnetic fieldsensor structure is aligned with the permanently magnetizable elementwith respect to the coil arrangement.
 4. The method according to claim1, wherein the magnetic field sensor structure comprises a magneticfield main sensor structure and an associated magnetic field auxiliarysensor structure, wherein detecting the test magnetic field andproviding a test signal based on the test magnetic field is performed bythe magnetic field auxiliary sensor structure.
 5. The method accordingto claim 1, wherein the magnetic field sensor structure comprises aplurality of magnetic field sensor elements, wherein detecting the testmagnetic field and providing a test signal based on the test magneticfield is performed such that individual signals of the magnetic fieldsensor elements or a combination signal generated from the individualsignals is provided as the test signal based on the test magnetic field.6. The method according to claim 1, wherein aligning the test magneticfield and the magnetic field sensor structure with the permanentlymagnetizable element comprises moving a soft magnetic element in thetest magnetic field.
 7. The method according to claim 1, wherein thealigning is performed such that the magnetic field distribution isaligned, within a tolerance range, perpendicular to a detection plane ofthe magnetic field sensor structure.
 8. The method according to claim 1,wherein detecting the test magnetic field and providing a test signalbased on the test magnetic field is performed with a giantmagnetoresistance (GMR), tunnel magnetoresistance (TMR) or anisotropicmagnetoresistance (AMR) sensor structure and/or a Hall sensor element asthe magnetic field sensor structure.
 9. An apparatus for magnetizing apermanently magnetizable element associated with a magnetic field sensorstructure, the apparatus comprising: means for generating a testmagnetic field penetrating the magnetic field sensor structure and thepermanently magnetizable element; means for detecting the test magneticfield and providing a test signal based on the test magnetic field bythe magnetic field sensor structure; means for aligning the testmagnetic field and the magnetic field sensor structure with thepermanently magnetizable element based on the test signal, until thetest signal reaches a set value corresponding to a predeterminedmagnetic field distribution with respect to the magnetic field sensorstructure; and means for generating a magnetizing field for permanentlymagnetizing the permanently magnetizable element, wherein themagnetizing field corresponds, within a tolerance range, to thepredetermined magnetic field distribution.
 10. The apparatus accordingto claim 9, wherein the means for generating a test magnetic field and amagnetizing field comprises a coil arrangement comprising one or severalair coils.
 11. The apparatus according to claim 9, wherein the magneticfield sensor structure comprises a magnetoresistive sensor structure.12. The apparatus according to claim 9, wherein the means for aligningis implemented to align the test magnetic field with the permanentlymagnetizable element with respect to the magnetic field sensorstructure, or the magnetic field sensor structure with the permanentlymagnetizable element with respect to the test magnetic field.
 13. Theapparatus according to claim 9, wherein the means for aligning furthercomprises a soft magnetic element and is implemented to move the softmagnetic element in the test magnetic field.
 14. The apparatus accordingto claim 9, wherein the magnetic field sensor structure comprises amagnetic field main sensor structure and an associated magnetic fieldauxiliary sensor structure, wherein the magnetic field auxiliary sensorstructure is implemented to detect the test magnetic field and toprovide a test signal based on the test magnetic field.
 15. Theapparatus according to claim 9, wherein the magnetic field sensorstructure comprises a plurality of magnetic field sensor elements,wherein the magnetic field sensor elements are implemented to detect thetest magnetic field and to provide a test signal, based on the testmagnetic field, as individual signals of the magnetic field sensorelements or as a combination signal generated from the individualsignals.
 16. The apparatus according to claim 9, wherein the set valueis selected such that the magnetic field distribution is aligned, withina tolerance range, perpendicular to a detection plane of the magneticfield sensor structure.
 17. A method of inscribing a definedmagnetization into a magnetoresistive sensor structure of a magneticfield sensor arrangement, which further comprises a magnetic fieldauxiliary sensor structure, the method comprising: generating a testmagnetic field penetrating the magnetic field sensor arrangement;detecting the test magnetic field and providing a test signal based onthe test magnetic field by the magnetic field auxiliary sensorstructure; aligning the test magnetic field and the magnetoresistivesensor structure to each other, until the test signal reaches a setvalue corresponding to a predetermined magnetic field distribution in adetection plane of the magnetic field auxiliary sensor structure;heating the magnetoresistive sensor structure to an inscriptiontemperature; and generating a magnetizing field for permanentlyinscribing the defined magnetization into the magnetoresistive sensorstructure, wherein the magnetizing field corresponds, within a tolerancerange, to the predetermined magnetic field distribution.
 18. The methodaccording to claim 17, wherein the magnetoresistive sensor structurecomprises a tunnel magnetoresistance (TMR), a giant magnetoresistance(GMR) or an anisotropic magnetoresistance (AMR) sensor structure. 19.The method according to claim 17, wherein aligning the test magneticfield is performed such that the magnetic field distribution isperpendicular, within a tolerance range, to the detection plane of themagnetic field auxiliary sensor structure.
 20. An apparatus forinscribing a defined magnetization into a magnetoresistive sensorstructure of a magnetic field sensor arrangement, which furthercomprises a magnetic field auxiliary sensor structure, the apparatuscomprising: means for generating a test magnetic field penetrating themagnetic field sensor arrangement; means for detecting the test magneticfield and providing a test signal based on the test magnetic field bythe magnetic field auxiliary sensor structure; means for aligning thetest magnetic field and the magnetoresistive sensor structure to eachother, based on the test signal, until the test signal reaches a setvalue corresponding to a predetermined magnetic field distribution in adetection plane of the magnetic field auxiliary sensor structure; meansfor heating the magnetoresistive sensor structure to an inscriptiontemperature; and means for generating a magnetizing field forpermanently inscribing the defined magnetization into themagnetoresistive sensor structure, wherein the magnetizing fieldcorresponds, within a tolerance range, to the predetermined magneticfield distribution.
 21. The apparatus according to claim 20, wherein themagnetoresistive sensor structure comprises a tunnel magnetoresistance(TMR), a giant magnetoresistance (GMR) or an anisotropicmagnetoresistance (AMR) sensor structure.
 22. The apparatus according toclaim 20, wherein the set value is selected such that the magnetic fielddistribution is aligned, within a tolerance range, perpendicular to thedetection plane of the magnetic field auxiliary sensor structure. 23.The method according to claim 1, comprising: monitoring the alignment ofa magnetic field of a reference magnet with respect to a magnetic fieldsensor structure comprising a magnetic field main sensor structure andan associated magnetic field auxiliary sensor structure, the monitoringcomprising: detecting the magnetic field penetrating the magnetic fieldsensor structure and providing a reference signal based on the magneticfield by the magnetic field auxiliary sensor structure; and determininga deviation of the alignment of the magnetic field of the referencemagnet by comparing the reference signal with a set signal correspondingto a predetermined magnetic field distribution of the magnetic field inthe detection plane of the magnetic field auxiliary sensor structure.24. The method according to claim 23, wherein the magnetic fieldauxiliary sensor structure is a Hall sensor, and the magnetic field mainsensor structure is a tunnel magnetoresistance (TMR), a giantmagnetoresistance (GMR) or an anisotropic magnetoresistance (AMR) sensorstructure.
 25. The method according to claim 1, further comprising:protecting a sensor arrangement comprising a sensor chip with thepermanently magnetizable element against an external primary magneticfield, the protecting further comprising: generating a secondarymagnetic field opposing the external primary magnetic field at thesensor chip.
 26. The method according to claim 25, wherein in generatingthe opposing secondary magnetic field, a compensation coil arrangedaround the sensor chip is electrically excited by a current proportionalto the external primary magnetic field.
 27. The method according toclaim 25, wherein a compensation coil and a primary coil are connectedin series and wherein in generating the opposing secondary magneticfield, the primary coil and the compensation coil carry the sameexcitation current.
 28. The method according to claim 25, whereingenerating the opposing secondary magnetic field is performed such thatparts of a metallic chip frame carrier on which the sensor chip isarranged, carry an appropriate current, so that the secondary magneticfield opposing the external primary magnetic field is generatedtangentially to a sensor chip surface.
 29. The method according to claim25, wherein generating the secondary magnetic field is performed suchthat the sensor chip is surrounded by a short-circuited compensationcoil, so that in a fast external primary magnetic field change asecondary magnetic field opposing the primary magnetic field isgenerated.
 30. The apparatus according to claim 9, further comprising: aprotective apparatus for protecting a sensor arrangement comprising asensor chip with the permanently magnetizable element against anexternal primary magnetic field, protective apparatus furthercomprising: a means for generating a secondary magnetic field opposingthe external primary magnetic field at the sensor chip.
 31. Theapparatus according to claim 30, wherein the means for generatingcomprises a compensation coil in which the sensor chip is arranged, andwherein the compensation coil carries an excitation current proportionalto the external primary magnetic field.
 32. The apparatus according toclaim 31, wherein the compensation coil is connected in series to aprimary coil generating the external primary magnetic field and carryingthe same excitation current.
 33. The apparatus according to claim 30,wherein the sensor chip is arranged on a metallic chip frame carrier,and parts of the metallic chip frame carrier are implemented such thatthe parts generate a secondary magnetic field opposing the externalprimary magnetic field tangentially to a sensor chip surface when theparts carry an appropriate excitation current.
 34. The apparatusaccording to claim 30, wherein the means for generating comprises ashort-circuited compensation coil in which the sensor chip is arranged.35. The apparatus according to claim 34, wherein the short-circuitcompensation coil is integrated in the sensor chip.
 36. The apparatusaccording to claim 35, wherein the short-circuit compensation coilintegrated in the sensor chip is implemented such that the sensor isfully covered and slightly overlapped by upper and lower metal sheetsconnected via contacts.
 37. The apparatus according to claim 36, whereinthe upper and lower metal sheets are connected to each other via atransistor.